Toner, method for manufacturing the toner, and image forming method and apparatus using the toner

ABSTRACT

A toner including toner particles including a binder resin and a release agent, wherein when the toner is molded into a plate upon application of a pressure of 478 kg/cm 2 , the toner plate has a surface having a coefficient of static friction of from 0.20 to 0.40. An image forming apparatus including an image bearing member, an image developer to form a toner image on the image bearing member, an image transferer configured to transfer the toner image on a receiving material and a fixer configured to fix the toner image thereon, wherein the apparatus has a waiting time not longer than 15 seconds, and a maximum power consumption not greater than 1.5 KW and 30 W in an image forming state and in a standby state, respectively, wherein the toner is the toner mentioned above.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a toner for developing anelectrostatic latent image formed by electrophotography, electrostaticrecording methods, electrostatic printing methods, etc. In addition, thepresent invention relates to a method for manufacturing the toner.Further, the present invention relates to an image forming method andapparatus using the toner.

[0003] 2. Discussion of the Background

[0004] As for electrophotography, various methods have been disclosed,for example, in U.S. Pat. No. 2,297,691 and Japanese Patent PublicationsNos. (hereinafter referred to as JPPs) 49-23910 and 43-24748. In thesemethods, a copy image is typically formed by the processes of forming anelectrostatic latent image on a photoreceptor including a photosensitivematerial by one of various latent image forming methods; developing thelatent image with a toner; transferring the toner image on a receivingmaterial such as papers; and fixing the toner image thereon uponapplication of heat, pressure or a solvent vapor.

[0005] The methods for developing an electrostatic latent image arebroadly classified into liquid developing methods using a liquiddeveloper in which one or more of pigments or dyes are finely dispersedin an insulating organic liquid, and dry developing methods, such ascascade developing methods, magnetic brush developing methods and powdercloud developing methods, which use a dry developer including a toner inwhich a colorant such as carbon black is dispersed in a natural orsynthetic resin. Currently, the dry developing methods are mainly usedbecause dry developers are easier to handle than liquid developers.

[0006] As for fixing methods in electrophotography, heat roller fixingmethods have been typically used because of having good energyefficiency. However, these heat roller fixing methods have a drawback inthat a so-called offset phenomenon tends to occur such that when a tonerimage is fixed, part of the toner image adheres to a heat roller and thepart of the toner image is re-transferred on a copy paper, resulting information of an undesired image.

[0007] In attempting to solve such an offset phenomenon, methods inwhich a release agent such as waxes is included in a toner have beendisclosed. For, example, Japanese Laid-Open Patent Publications Nos.(hereinafter JOPs) 51-143333, 57-148752, 58-97056 and 60-247250 havedisclosed to use solid silicone varnishes, higher fatty acids, higheralcohols, various waxes, etc., as a release agent.

[0008] However, when such a release agent is included in a toner, afilming problem tends to occur in that the release agent is separatedfrom the toner when developing processes are performed and then the thusformed free release agent adheres to a photoreceptor and a developingsleeve. The thus formed film of the free release agent gradually growswhen copying processes are repeated, resulting in formation of a whitestripe image on a half tone image when the film becomes too thick.Therefore, it has been needed for a toner including a release agent tosolve the offset phenomenon and filming problem at the same time. Inother words, in order to produce images having good image qualities fora long period of time, it has been needed to improve toners while payingattention to the release agent therein.

[0009] Currently, a need for high quality images increases more and morein the market. Satisfactory images cannot be produced by conventionaltoners, which typically have a volume average particle diameter of from10 to 15 μm, and therefore a need exists for a toner having a smallerparticle diameter. However, when the particle diameter of a tonerbecomes smaller, the release agent included in the toner is easilyseparated from the toner if the toner is subjected to stresses, etc. Inparticular, when the toner is prepared by a pulverization method,kneaded toner constituents tend to be divided at the position in whichthe release agent is present when pulverized, which typically has asharp molecular weight distribution peak and is brittle, and thereby therelease agent tends to be present on the surface of the resultant tonerparticles or tends to be present as fine powders in the resultant toner.Therefore, when a toner having a small particle diameter is used toproduce high quality images, the filming problem tends to occur. Inaddition, another problem of poor fixing occurs. Namely, when a tonerhaving a small particle diameter is used, the amount of the tonerincluded in a half tone image formed on a receiving material decreases.In this case, the amount of heat applied from a heating member to thetoner particles transferred on a recessed portion of the receivingmaterial is very small, and therefore the toner image has poorly fixedparticularly when fixed at a low temperature.

[0010] In addition, in order to save power consumption and reduce CO₂emission, there are needs for image forming apparatus to reduce thewaiting time (warm-up time), i.e., an interval between the time when theimage forming apparatus is in an on state to the time when an imageforming operation can be performed, and to minimize the energy consumedin the pre-heating state of the apparatus in which the fixing unit ispreliminarily heated so as to be quickly heated to a temperature in thefixable temperature range when receiving a print order.

[0011] There is a technique procurement project for next-generationcopiers in the DSM (Demand-side Management) program of the year 1999 ofInternational Energy Agency, and requirements for the copiers aredisclosed. As for the requirements for a copier having a copying speednot less than 30 cpm, the waiting time is not greater than 10 secondsand the power consumption in the waiting period (i.e., a period in whichimage forming operations are not performed) is from 10 to 30 W, whichdepends on the copying speed. Thus, there are stringent requirements forthe next generation copiers to drastically reduce total electric powerconsumption and CO₂ emission.

[0012] A method in which a heat roller having a low heat capacity isused to improve its temperature sensitivity is considered to be usefulfor satisfying the requirements. However, the method is not satisfactorybecause in medium-speed to high-speed image forming apparatus, theamount of heat applied to toner images is very small.

[0013] In order to fulfill the above-mentioned requirements, i.e., tominimize the waiting time, it is considered that to lower the fixabletemperature of the toner itself is needed.

[0014] When the level of low temperature fixing is discussed referringto the preset fixing temperature of the image forming apparatus, theimage forming apparatus are needed to have a preset fixing temperaturelower than the preset fixing temperature at which a current low fixabletoner can be used. Therefore it is considered that a toner satisfyingthe requirements cannot be easily developed only by using knowntechniques.

[0015] In addition, when a toner having low temperature fixability isused, it is considered that to impart a wide fixable temperature range(i.e., a hot-offset resistance) and a good high temperaturepreservability to the toner become difficult.

[0016] In particular, when the image forming speed increases, thetemperature of the heating member tends to decrease in fixing, resultingin decrease of the amount of heat used for fixing. Therefore, measuresshould be taken on both the toner and fixing device sides to improve lowtemperature fixability.

[0017] In attempting to solve these problems, various methods have beenproposed. For example, JOP 5-173354 discloses atoner including a releaseagent, wherein the physical properties, addition amount and species ofthe release agent are specified. JOP 6-161144 discloses a tonerincluding a release agent, wherein the shape of the release agentdispersed in the toner is specified. JOP 7-104500 (i.e., Japanese PatentNo. 2,675,974) discloses a toner having a specific coefficient ofdynamic friction and including an external additive treated with apolyalkylene and a silicone oil to improve the cleaning ability anddurability of the toner.

[0018] JPP 8-3656 discloses a toner system including two differentmagnetic toners having different coefficients of dynamic friction. JOP11-95477 discloses a toner including an external additive having acoefficient of dynamic friction of from 0.12 to 0.30 to improve thetransferability of the toner and to avoid the filming problem. JOP2000-105484 discloses a technique in which the coefficient of staticfriction of a toner image is specified to improve the fixability of thetoner image. JOP 2000-310875 discloses a toner whose coefficient offriction is specified when the external additive of the toner isembedded into the toner by stresses. In addition, JOP 2001-5220discloses four color toners for forming full color images, wherein thecoefficients of dynamic friction are specified.

[0019] However, both the filming problem and the offset problem can besolved at the same time by these toners and methods. In particular, whenthe toners are subjected to mechanical stresses and heat stresses inimage forming apparatus, the effects thereof are hardly exerted, i.e.,the filming problem occurs when used for long period of time. Therefore,a need exists for a technique by which the filming problem and theoffset problem can be avoided at the same time even when a toner is usedfor a long period.

[0020] In attempting to improve low temperature fixability of toner,several methods in which two different polyester resins having differentproperties are used in a toner have been proposed. For example, a methodin which a non-linear polyester resin is used in combination with alinear polyester resin (JOP 60-90344); a method in which a crosslinkablepolyester having a glass transition temperature (Tg) not lower than 50°C. and a softening point not higher than 200° C. is used in combinationwith a linear polyester resin having a softening point not higher than150° C. and a weight average molecular weight (MW) of from 3,000 to50,000 (JOP 64-15755); a method in which a non-linear polyester polymerhaving a weight average molecular weight not less than 5,000 and avariance ratio (MW/MN) not less than 20 is used in combination with anon-linear polyester polymer having a weight average molecular weight offrom 1,000 to 5,000 and a variance ratio not less than 4 (JOP 2-82267);a method in which an organic metal compound including a linear polyesterresin having an acid value of from 5 to 60 and a non-linear polyesterresin having an acid value less than 5 is included in a toner (JOP3-229264); a method in which a first saturated polyester resin is usedin combination with a second saturated polyester resin having an acidvalue 1.5 or more times the acid value of the first polyester resin (JOP3-41470); etc.

[0021] In these methods, it is intended to achieve a good combination oflow temperature fixability and hot offset resistance by using a mixtureof a non-crosslinkable resin with a crosslinkable resin. However, theblended resins have good compatibility (i.e., the resins can be mixedwell with each other), and therefore the kneaded toner constituentscannot be easily pulverized, resulting in deterioration of productivity,and thereby the manufacturing costs increase.

[0022] In addition, toners in which a polyester resin having goodfixability is mixed with a styrene-acrylic resin having goodpulverizability have been disclosed in JOPs 49-6931 and 54-11424.However, since polyester resins typically have poor compatibility withstyrene-acrylic resins, both the resins are unevenly dispersed in atoner when the resins are simply mixed mechanically. Therefore when atoner is prepared, a colorant such as carbon black and a chargecontrolling agent are poorly dispersed in the toner, resulting inoccurrence of fouling in the background areas of the resultant tonerimages.

[0023] JOPs 4-142301 and 7-98517 have proposed methods in which a resinprepared by polymerizing a polyester resin with a styrene resin in acontainer is used for a toner to impart a good pulverizability to thetoner and to uniformly disperse a colorant and a charge controllingagent in the resin. However, these toners have a narrower fixabletemperature range than in the case in which a non-linear resin and alinear resin are used in combination. In attempting to solve thisproblem, JOP 8-320593 discloses a toner which includes a mixture ofthree different resins having different physical properties, i.e.,different glass transition temperatures. When preparing this toner,toner constituents cannot be dispersed well because the resins aremerely blended, and thereby problems occur such that background foulingis caused in the resultant images and in addition the toner image haspoor blocking resistance.

[0024] As mentioned above, currently low temperature fixing areincreasingly performed, and therefore a need exists for low temperaturefixing technique. In addition, a need also exists for a miniaturizedimage forming apparatus. However, there is no toner which has a lowtemperature fixability and a wide fixable temperature range (i.e., goodhot offset resistance) as well as good high temperature preservabilityand good pulverizability, and is capable of producing images having goodimage qualities without producing background fouling and the filmingproblem even when a low pressure fixing device is used.

[0025] Because of these reasons, a need exists for a toner fulfillingthe requirements mentioned above. In addition, a need exists for animage forming method and apparatus, in which high quality toner imagesare produced for a long period of time without causing the filmingproblem and offset problem while electric power consumption and waitingperiod are reduced.

SUMMARY OF THE INVENTION

[0026] Accordingly, an object of the present invention is to provide atoner which can be used for a long period of time without forming tonerfilm on an image bearing member, etc. and without causing a hot offsetproblem even when the toner is subjected to mechanical and heatstresses, and a method for manufacturing the toner.

[0027] Another object of the present invention is to provide a tonerwhich can produce images having good fine line reproducibility withoutcausing background fouling, and a method for manufacturing the toner.

[0028] Yet another object of the present invention is to provide a tonerhaving a good low temperature fixability and good high temperaturepreservability, and a method for manufacturing the toner.

[0029] A further object of the present invention is to provide a tonerwhich can produce good images even when used for a small-size imageforming apparatus in which a toner replenishing mechanism and a tonerconcentration sensor are not provided, and a method for manufacturingthe toner.

[0030] A still further object of the present invention is to provide animage forming method and apparatus by which good images can be producedat a low fixing temperature without causing a filming problem and a hotoffset problem while electric power consumption and waiting period arereduced.

[0031] Briefly these objects and other objects of the present inventionas hereinafter will become more readily apparent can be attained by atoner composition including toner particles, which particles include atleast a binder resin and a release agent, wherein when the tonercomposition is pressed upon application of a pressure of 478 kg/cm² toform a toner plate, the toner plate has a surface having a coefficientof static friction of from 0.20 to 0.40.

[0032] The toner particles preferably have a volume average particlediameter (D4) of from 4.0 to 7.5 μm, and includes particles having aparticle diameter not greater than 5.0 μm in an amount of from 60 to 80%by number.

[0033] The release agent is preferably a material selected from thegroup consisting of carnauba waxes, montan waxes and oxidized ricewaxes, and is preferably present in the toner particles in an amount offrom 2 to 10% by weight based on the binder resin in the tonerparticles.

[0034] When the release agent is dispersed in the binder resin, therelease agent preferably has a volume average particle diameter of from10 to 800 μm.

[0035] The binder resin preferably includes a non-linear polymer (A), alinear polymer (B) and a polymer (C) which is prepared by performing acondensation polymerization and addition polymerization at the same timein a container using a mixture of a condensation-polymerizable monomerand an addition-polymerizable monomer or performing a condensationpolymerization and addition polymerization independently in a containerusing a mixture of a condensation-polymerizable monomer and anaddition-polymerizable monomer.

[0036] Each of the polymers (A), (B) and (C) preferably has a polyesterunit or a polyamide unit.

[0037] The toner composition may be a magnetic toner compositionincluding a magnetic material.

[0038] In another aspect of the present invention, a method formanufacturing a toner composition including the steps of kneading amixture including at least a non-linear polymer (A), a linear polymer(B)., a polymer (C) and a release agent upon application of heat;cooling the kneaded mixture; pulverizing the mixture; and classifyingthe pulverized mixture to prepare toner particles, wherein the polymer(C) is prepared by performing a condensation polymerization and additionpolymerization at the same time in a container using a mixture of acondensation-polymerizable monomer and an addition-polymerizable monomeror performing a condensation polymerization and addition polymerizationindependently in a container using a mixture of acondensation-polymerizable monomer and an addition-polymerizablemonomer.

[0039] In yet another aspect of the present invention, an image formingapparatus is provided which includes an image bearing member configuredto bear an electrostatic latent image thereon, an image developerconfigured to develop the latent image with a developer including atoner to form a toner image on the image bearing member, an imagetransferer configured to transfer the toner image onto a receivingmaterial optionally via an intermediate transfer medium, and a fixerconfigured to fix the toner image on the receiving material, wherein thewaiting time of the image forming apparatus is not longer than 15seconds, and preferably not longer than 10 seconds; the maximum electricpower consumption of the image forming apparatus is not greater than 1.5KW when image forming operations are performed; and the maximum electricpower consumption is not greater than 30 W when image forming operationsare not performed, wherein the toner is the toner composition of thepresent invention.

[0040] The image forming apparatus preferably has a copy speed of 30cpm/A-4 size.

[0041] The developer preferably includes a carrier and the tonercomposition. In addition, the image forming apparatus preferablyincludes a toner container including the toner composition to bereplenished and/or a developer container including the toner compositionand a carrier.

[0042] In a further aspect of the present invention, an image formingmethod is provided which includes steps of forming a toner image on areceiving material; and passing the receiving material through a nipbetween two fixing members upon application of heat and pressure theretoto fix the toner image on the receiving material, wherein the thicknessof the fixing member contacting the toner image is not greater than 0.7mm and the pressure (i.e., (load applied to the members)/(contactingarea thereof)) applied to the two fixing members is not greater than1.5×10⁵ Pa.

[0043] In a still further aspect of the present invention, an imageforming method is provided which includes steps of forming a toner imageon a receiving material; and passing the receiving material through anip between a fixing belt member which is heated by a fixed heater and apressing member which presses the receiving material toward the heatingbelt member to fix the toner image on the receiving material, whereinthe toner image is formed of the toner composition of the presentinvention.

[0044] In a still further aspect of the present invention, an imagedeveloper is provided which includes a developer bearing member having amagnetic field generating means therein and configured to bear adeveloper including a magnetic carrier and a magnetic toner compositionincluding a binder, a release agent and a magnetic material, whilerotating; a first regulation member configured to regulate the amount ofthe developer supplied to the developer bearing member to form adeveloper layer on the developer bearing member; a developer containingmember configured to contain the developer regulated by the firstregulating member; and a toner containing member located adjacent to thedeveloper containing member and configured to supply the tonercomposition to the developer bearing member through an opening, whereinthe image developer changes the amount of the toner supplied from thetoner containing member according to information of a tonerconcentration in the developer layer on the developer bearing member,wherein the developer containing member includes a second regulatingmember which is located on an upstream side from the first regulatingmember relative to the rotating direction of the developer bearingmember, and configured to scrape the developer layer when the tonerconcentration of the developer layer increases and the developer layerthickens to cover the opening with the scraped developer, and whereinthe toner composition is the toner composition of the present invention.

[0045] These and other objects, features and advantages of the presentinvention will become apparent upon consideration of the followingdescription of the preferred embodiments of the present invention takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Various other objects, features and attendant advantages of thepresent invention will be more fully appreciated as the same becomesbetter understood from the detailed description when considered inconnection with the accompanying drawings in which like referencecharacters designate like corresponding parts throughout and wherein:

[0047]FIG. 1 is a graph illustrating changes of the temperature of thefixing member of an embodiment of the image forming apparatus of thepresent invention;

[0048]FIG. 2 is a graph illustrating changes of the electric powerconsumption of the above embodiment of the image forming apparatus ofthe present invention;

[0049] FIGS. 3 to 6 are schematic views illustrating embodiments of thefixing device of the image forming apparatus of the present invention;

[0050]FIG. 7 is a schematic view illustrating an embodiment of the imagedeveloper of the image forming apparatus of the present invention; and

[0051] FIGS. 8 to 10 are schematic views for explaining the behavior ofthe developer in the above image developer.

DETAILED DESCRIPTION OF THE INVENTION

[0052] The present invention will be explained in detail.

[0053] The present inventors have been attempting to prevent the filmingproblem while paying attention to the release agent present on a surfaceof toner particles. In particular, the present inventors attempt toprevent the filming problem while taking consideration of the stressesapplied to the toner in an image forming apparatus. As a result, it isfound that by using a toner composition having a property such that whenthe toner composition is molded into a toner plate upon application of apressure of 478 kg/cm², the toner plate has a surface having acoefficient of static friction of from 0.20 to 0.40, the filming problemcan be avoided even when the stresses are applied to the toner.

[0054] In the present invention, the toner composition (hereinafterreferred to as toner) means a composition that includes toner particlesincluding at least a binder resin and a release agent, and one or moreexternal additives. The coefficient of static friction is measured for atoner plate of the toner composition. The toner plate is formed bypressing the toner composition upon application of 6 tons per 12.56 cm²(i.e., 478 kg/cm²) to form a toner plate.

[0055] The toner of the present invention is prepared by kneading amixture including at least a binder resin and a release agent using aheat roll mill upon application of heat; cooling the kneaded mixture;pulverizing the mixture; classifying the pulverized mixture to formtoner particles; and mixing an external additive with the tonerparticles using a Henshel mixer or the like.

[0056] The feature of the toner of the present invention is that whenthe toner is molded into a toner plate upon application of pressure of478 kg/cm², the surface friction coefficient of the plate ranges from0.20 to 0.40, preferably from 0.25 to 0.35, and more preferably from0.30 to 0.35. The filming problem to be solved by the present inventionis that a release agent included in a toner is transferred on thesurface of a photoreceptor or a developing sleeve. In order to solvethis filming problem, the amount of a release agent present on thesurface of toner particles should be controlled.

[0057] In general, release agents have a low friction coefficient. Themore the amount of a release agent present on the surface of a toner,the lower the friction coefficient of the surface of the toner. Inaddition, when an external additive of a toner, which serves as a spacer(i.e., covers the surface of the toner), is embedded in the toner due tophysical stresses, the surface of the toner particles are exposed (i.e.,the release agent is present on the surface of the toner), and therebythe friction coefficient of the surface of the toner particles lowers.

[0058] In the present invention, the friction coefficient of a toner ismeasured by the following method. At first, a toner is molded into aplate upon application of pressure. The surface of the toner plate isanalyzed by a friction analyzer to determine the friction coefficient ofthe toner plate. When this measurement is performed (i.e., a pressure isapplied to the toner), the toner is subjected to mechanical and heatstresses, which are similar to the stresses which the toner is subjectedin an image forming apparatus, and therefore the release agent includedin the toner tends to separate from the toner, resulting inmigration ofthe release agent to the surface of the toner. Namely, the lower thefriction coefficient of the toner plate, the more the amount of therelease agent present on the surface of the toner. Therefore, byperforming this measurement, it can be determined whether the toner isstable when repeatedly used.

[0059] When the friction coefficient of a toner-including a releaseagent is not less than 0.20, i.e., when the amount of the release agentpresent on the surface of the toner is small, the filming problem can beprevented even when used for a long period of time.

[0060] In addition, when the friction coefficient is not greater than0.4, the hot offset problem can be prevented because the release agentfully fulfills its function (i.e., exerts the releasability).

[0061] The friction coefficient of a toner including a release agentdepends on the amount of the release agent present on the surface of thetoner. The friction coefficient of a toner changes depending on whetherthe release agent is present on the surface of the toner when the toneris prepared by pulverizing a toner block and the adhesion conditions ofthe external additive on the toner. The amount of the release agent onthe toner surface changes depending on the particle diameter of therelease agent when the toner constituents including the release agentare kneaded, and pulverization conditions.

[0062] In general, release agents are more brittle than binder resins.Therefore, when a kneaded toner block including a release agent ispulverized, the toner block tends to be divided at the release agentportion and therefore the release agent tends to be present on thesurface of the resultant toner particles. In addition, the release agenttends to be present as fine particles in the toner. Therefore, by makingthe diameter of the release agent to be dispersed in the toner blocksmall (by changing the addition amount of the release agent, theparticle diameter of the release agent added, compatibility of binderresins used, and kneading conditions such as shear strength applied inthe kneading step), the amount of the release agent present on the tonerparticles can be decreased. In addition, since the friction coefficientof external additives is typically greater than that of release agents,the friction coefficient of a toner can be controlled by changing thecoverage of the toner with an external additive and the adhesionconditions of the external additive.

[0063] The properties of a toner including a release agent largelychange depending on the dispersing conditions of the release agent inthe toner block. When a release agent is dispersed in a toner blockwhile having a small dispersion diameter, the concentration of therelease agent on the surface of the resultant toner particles is almostthe same as that in the toner block. However, when a release agent isdispersed in a toner block while having a large dispersion diameter, theconcentration of the release agent on the surface of the resultant tonerparticles is greater than that in the toner block. The reason isconsidered to be as follows.

[0064] When a kneaded toner block is pulverized, pulverization istypically performed using a mechanical impact force, an impact forceusing jet air, etc. When an external force is applied to a toner, thetoner block is pulverized (divided) at weak portions (i.e., at therelease agent portions). Therefore, when the release agent is present inthe toner block while having a large dispersion diameter, the amount ofthe release agent on the surface of the resultant toner particlesincrease or fine release agent particles increase in the resultant tonerparticles. Therefore, such a toner tends to cause the filming problem.Such a toner has a low coefficient of dynamic friction. However, bycontrolling the frictional coefficient of a toner so as to fall in theabove-mentioned range, the toner capable of producing high qualityimages without causing the filming problem and hot offset problem can beprovided.

[0065] In the present invention, friction coefficient is measured usingan automatic friction/abrasion analyzer DFPM-SS manufactured by KyowaInterface Science Co., Ltd. By using this instrument and a stainlesssteel ball as a contact member, the coefficient of static friction of atoner (a toner plate) can be determined.

[0066] In addition, when the toner of the present invention has aparticle diameter distribution such that the volume average particlediameter (D4) of the toner particles ranges from 4.0 to 7.5 μm and inaddition particles having a particle diameter not greater than 5.0 μmare present in an amount of from 60 to 80% by number, the toner canproduce images having good fine-line and half-tone reproducibility.Preferably the D4 is from 5.0 of 7.0 μm, and the content of theparticles having a particle diameter not greater than 5.0 μm is from 65to 75% by number. When a toner has such properties, not only highdefinition images can be produced, but also the filming problem, whichis caused because a large amount of the release agent is present on thetoner surface, can be prevented (i.e., the toner has good durability). Atoner having such a desired particle diameter distribution can beprepared by controlling, for example, the following factors:

[0067] (1) The amount of the kneaded toner block to be pulverizedsupplied to a pulverizer;

[0068] (2) pressure and flow rate of high pressure air used forpulverizing the kneaded toner block;

[0069] (3) shape of a collision plate used for pulverizing the kneadedtoner block;

[0070] (4) position from which air is supplied and air flowing directionin the air classifier used; and

[0071] (5) pressure of an exhaust fan in the air classifier used.

[0072] In the present invention, the volume average particle diameter(D4) and the content of particles having a particle diameter not greaterthan 5.0 μm are determined using a system including a Coulter CounterTA-II manufactured by Coulter Electronics, Inc., an interface (fromNikkaki-Bios Co., Ltd.) capable of outputting a number average particlediameter distribution and a volume average particle diameter, and apersonal computer PC9801 from NEC Corp. As the electrolyte, 1% NaClaqueous solution which is prepared using a sodium chloride of class 1 isused. The measuring method is as follows.

[0073] (1) 0.1 to 5 ml of a surfactant serving as a dispersant(preferably an alkylbenzenesulfonic acid salt) is added to 50 to 100 mlof the electrolyte mentioned above;

[0074] (2) 1 to 10 mg of a sample to be measured is added to theelectrolyte including the surfactant;

[0075] (3) the mixture is dispersed for 1 minute using an ultrasonicdispersing machine;

[0076] (4) 100 to 200 ml of the electrolyte is contained in anothercontainer and the dispersion prepared above is added thereto such thatthe concentration of the sample is a predetermined value; and

[0077] (5) the particle diameter distribution of 30,000 particles havinga particle diameter of from 2 to 40 μm of the sample is measured usingCoulter Counter TA-II and an aperture of 100 μm to determine the volumeand number particle diameter distributions of the particles.

[0078] The volume average particle diameter on a weight basis isdetermined by using the volume particle diameter distribution.

[0079] As the release agent for use in the toner of the presentinvention, known release agents can be used. Among the release agents,carnauba waxes, montan waxes and oxidized rice waxes are preferably usedalone or in combination.

[0080] Suitable carnauba waxes include ones which have microcrystal, andan acid value not greater than 5. In addition, it is preferable thatwhen carnauba wax is dispersed in a binder resin, the particle diameterof the carnauba wax is preferably not greater than 1 μm.

[0081] Montan waxes are montan-type waxes prepared by refining minerals.Suitable montan waxes include ones which have microcrystal, and an acidvalue of from 5 to 14 mgKOH/g.

[0082] Oxidized rice waxes are prepared by air-oxidizing rice waxes.Suitable oxidized rice waxes include ones which have an acid value offrom 10 to 30 mgKOH/g.

[0083] Other known release agents such as solid silicone varnishes,higher fatty acids, higher alcohols, montan ester waxes,low-molecular-weight polypropylene waxes, etc. can be used incombination with the above-mentioned suitable release agents.

[0084] The content of the release agent in the toner is typically from 1to 15 parts by weight, and preferably from 2 to 10 parts by weight, per100 parts by weight of the binder resin included in the toner to controlthe amount of the release agent present on the surface of the toner,i.e., to prevent the filming and hot-offset problems. The amount of therelease agent present on the surface of the toner (i.e., the dispersiondiameter of the release agent in the toner block) can be controlled bychanging addition amount of the release agent, shear strength applied tothe toner constituents in kneading, and the kneading conditions such askneading temperature.

[0085] In the present invention, the particle diameter of a releaseagent before the release agent is added to a binder resin is from 10 μmto 1 mm, and preferably from 10 to 800 μm to control the amount of therelease agent present on the surface of the toner, i.e., to prevent thefilming and hot-offset problems. The particle diameter of the releaseagent is measured by a laser diffraction/scattering particle diametermeasuring instrument LA-920 manufactured by Horiba, Ltd.

[0086] As the binder resin for use in the toner of the presentinvention, known binder resins for use in the conventional toners can beused. However, it is preferable to use a combination of the followingpolymers (A), (B) and (C):

[0087] (A) a non-linear polymer;

[0088] (B) a linear polymer; and

[0089] (C) a polymer (hereinafter sometimes referred to as a hybridresin) which is prepared by performing a condensation polymerization andaddition polymerization at the same time in a container using a mixtureof a condensation-polymerizable monomer and an addition-polymerizablemonomer, or performing a condensation polymerization and additionpolymerization independently in a container using a mixture of acondensation-polymerizable monomer and an addition-polymerizablemonomer.

[0090] In addition, it is preferable that the polymers (A), (B) and (C)have a polymer unit of the same kind. When such a binder resin is used,the dispersion of the release agent in the toner of the presentinvention can be further improved and therefore the filming problem canbe prevented. In addition, the resultant toner has a wide fixabletemperature range and good high temperature preservability (i.e., goodblocking resistance), and can produce good images without backgroundfouling.

[0091] A mixture including such binder resins and a release agent iskneaded upon application of heat, cooled, pulverized, and classified toprepare toner particles.

[0092] In order to prepare an improved low temperature fixable toner(i.e., to save fixing energy), it is preferable to use a combination ofa linear polymer (B) having a low temperature fixability with anon-linear polymer (A) having good hot offset resistance, wherein thepolymers (A) and (B) include a polymer of the same kind, because thepolymers can be well dispersed in the resultant toner and the resultanttoner has a wide fixable temperature range.

[0093] However, when a mixture of polymers having low temperaturefixability is used, it is hard to pulverize the resultant toner blockand therefore the toner has poor productivity because the polymers aresoft and mixed well with each other. In addition, the resultant tone haspoor high temperature preservability (i.e., poor blocking resistance).

[0094] In order to improve pulverizability, it has been attempted to usea combination of a resin having different compatibility with other twodifferent resins (for example, a combination of a styrene-acrylic resinwith a linear polyester and a non-linear polyester). However, in theresultant toner the release agent and colorant are poorly dispersed,resulting in formation of background fouling in the resultant images.

[0095] In contrast, in the present invention a hybrid resin (C) whichincludes a polymer unit of the same kind of the polymer unit included inthe polymers (A) and (B) is added to the polymers (A) and (B). In such atoner, the hybrid resin (C) has a proper compatibility with the polymers(A) and (B), and therefore a toner which has a wide fixable temperaturerange and can produce good images without background fouling whilehaving a good pulverizability and good high temperature preservabilitycan be provided. When the polymers (A), (B) and (C) have a polymer unitof the same kind, the resultant toner has further improved hightemperature preservability (blocking resistance) and can produce imagesfurther improved in view of background fouling.

[0096] The polymers (A), (B) and (C) preferably have a polyester unit ora polyamide unit, and more preferably have a polyester unit.

[0097] The contents of the non-linear polymer (A), linear polymer (B)and hybrid resin (C) in the toner are from 30 to 70 parts by weight,from 30 to 70 parts by weight and from 5 to 30 parts by weight,respectively, per 100 parts by weight of total weight of the polymers(A), (B) and (C).

[0098] In addition, it is preferable that the following relationshipsare satisfied because the resultant toner has a further wide fixabletemperature range and better pulverizability.

Tm(A)>Tm(C)>Tm(B)  (1)

|Tg(A)−Tg(B)|<10(° C.)  (2)

30≦Tm(A)−Tm(B)≦60(° C.)  (3)

[0099] wherein Tm(A), Tm(B) and Tm(C) represent softening points of thepolymers (A), (B) and (C), respectively, and Tg(A) and Tg(B) representglass transition temperatures of the polymers (A) and (B), respectively.

[0100] When the relationship (1) is satisfied, background fouling of theresultant images can be improved. The reason is considered to be thatthe non-linear polymer (A) and the linear polymer (B) are well dispersedby the hybrid polymer (C)

[0101] When the relationship (2) is satisfied, the binder resins can bemixed well in the kneading process and therefore the resins aredispersed well, resulting in improvement of background fouling. In therelationship (2), the value of |Tg(A)−Tg(B)| is preferably not greaterthan 7° C.

[0102] When the relationship (3) is satisfied, the resultant toner has awide fixable temperature range. The difference (i.e., Tm(A)−Tm(B)) ispreferably from 35 to 55° C.

[0103] In addition, when the non-linear polymer (A) has an acid value offrom 20 to 70 mgKOH/g and/or the linear polymer (B) has an acid value offrom 7 to 70 mgKOH/g, the resultant toner has good low temperaturefixability and exhibits high stability to withstand environmentalconditions. The reason is considered to be that the resins has affinityfor receiving materials when the acid values of the polymers (A) and (B)are not less than 20 or 7 mgKOH/g, respectively, and therefore the tonercan be fixed at a lower temperature. In addition, when the acid valuesof the polymers (A) and (B) are not greater than 70 mgKOH/g, theresultant toner can stably maintain a charge without being influenced byhumidity changes. Therefore, images having high image density can beproduced independently of environmental conditions.

[0104] In the present invention, by including a salicylic acid metalcompound, which metal has a 3-valence or more, in the toner, the hotoffset resistance can be improved because the metal salt reacts with thereactive portions of the resins and release agent, resulting information of a lightly-crosslinked structure. When the metal has a2-valence or less, the hot offset resistance cannot be improved becausethe reaction product has a two-dimensional structure.

[0105] When the content of a salicylic acid metal compound in the toneris from 0.05 to 10 parts by weight per 100 parts by weight of the binderresin used, the effect for preventing the hot offset problem can beexerted. When the content is less than 0.05 parts by weight, the offsetpreventing effect cannot be exerted. To the contrary, when the contentis greater than 10 parts by weight, low temperature fixabilitydeteriorates although the hot offset resistance is further improved.

[0106] In addition, when the non-linear polymer (A) has a hydroxyl valuenot less than 20 mgKOH/g, the resultant toner has good hot offsetresistance. The reason is considered to be that the hydroxyl groups ofthe non-linear polymer (A) react with a reactive portion of thesalicylic acid metal complex, resulting in formation of athree-dimensional weak crosslinking network.

[0107] Next, toner constituents for use in the toner of the presentinvention will be explained in detail.

[0108] Suitable polymers for use in the polymers (A), (B) and (C)include polymers prepared by condensation polymerization, such aspolyesters and polyamides, polymers prepared by addition polymerization,such as styrene-acrylic copolymers and styrene-butadiene copolymers.However, the polymers (A), (B) and (C) are not limited thereto, and anyknown polymers which are prepared by condensation polymerization oraddition polymerization can be used.

[0109] Specific examples of the polymers prepared by condensationpolymerization include polyester resins, polyester-polyamide resins,polyamide resins, etc. Suitable polyester resins for use in the toner ofthe present invention include polymers prepared bycondensation-polymerizing a polyhydric hydroxyl compound with apolybasic acid. Specific examples of the polyhydric hydroxyl compoundsinclude glycols such as ethylene glycol, diethylene glycol, triethyleneglycol and propylene glycol; alicyclic compounds having two hydroxylgroups such as 1,4-bis(hydroxymethyl)cyclohexane; dihydric phenolcompounds such as bisphenol A; etc. In addition, compounds having threeor more hydroxyl groups can also be used as the polyhydric hydroxylcompound.

[0110] Specific examples of the polybasic acids include dibasic acidssuch as maleic acid, fumaric acid, phthalic acid, isophthalic acid,terephthalic acid, succinic acid and malonic acid; polybasic carboxylicacid monomers such as 1,2,4-benzenetricarboxylic acid,1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid,1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid,1,3-dicarboxyl-2-methylenecarboxypropane and1,2,7,8-octanetetracarboxylic acid; etc.

[0111] Suitable monomers for use in the polyester-polyamide resins andpolyamide resins include polyamines such as ethylenediamine,pentamethylenediamine, hexamethylenediamine, phenylenediamine andtriethylenetetramine; aminocarboxylic acids such as 6-aminocaproic acidand ε-caprolactam; etc. The polyester-polyamide resins and polyamideresins for use in the present invention preferably have a glasstransition temperature not lower than 55° C., and more preferably notlower than 57° C.

[0112] Suitable polymers prepared by addition polymerization for use inthe toner of the present invention include vinyl resins prepared byradical polymerization, but are not limited thereto. Specific examplesof the monomers for use in the polymers prepared by additionpolymerization include styrene type monomers such as styrene,o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene,p-ethylstyrene, vinylnaphthalene; ethylene type unsaturated mono-olefinssuch as ethylene, propylene, butylene and isobutylene; vinyl esters suchas vinyl chloride, vinyl bromide, vinyl acetate and vinyl formate;ethylene type monocarboxylic acids and their esters such as acrylicacid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropylacrylate, tert-butyl acrylate, amyl acrylate, methacrylic acid, methylmethacrylate, ethyl methacrylate, n-propyl methacrylate, isopropylmethacrylate, tert-butyl methacrylate, amyl methacrylate, stearylmethacrylate, methoxy ethyl methacrylate, glycidyl methacrylate, phenylmethacrylate, dimethylaminoethyl methacrylate and diethylaminoethylmethacrylate; ethylene type monocarboxylic acid substitution compoundssuch as acrylonitrile, methacrylonitrile and acrylamide; ethylene typedicarboxylic acids and their substitution compounds such as dimethylmaleate; and vinyl ketones such as vinyl methyl ketone.

[0113] In addition, a crosslinking agent can be added when additionpolymerization is performed. Specific examples of the crosslinkingagents for use in the addition polymerization include known crosslinkingagents such as divinyl benzene, divinyl naphthalene, polyethyleneglycoldimethacrylate, diethyleneglycol dimethacrylate, triethyleneglycoldiacrylate, diprophleneglycol dimethacrylate, polypropyleneglycoldimethacrylate, and diallyl phthalate.

[0114] The addition amount of the crosslinking agent is 0.05 to 15 partsby weight, and preferably from 0.1 to 10 parts by weight, per 100 partsby weight of monomers used. When the addition amount of the crosslinkingagent is less than 0.05 parts by weight, the effect of the crosslinkingagent cannot be exerted. When the addition amount is greater than 15parts by weight, the resultant resin cannot be melted even uponapplication of heat, and therefore the resultant toner produces poorlyfixed images when the toner images are fixed upon application of heat.

[0115] When an addition-polymerizable monomer is polymerized, apolymerization initiator is typically used. For example, azo type ordiazo type initiators such as 2,2-azobis(2,4-dimethylvaleronitrile) and2,2-azobisisobutylonitrile, or peroxide polymerization initiators suchas benzoyl peroxide, methyl ethyl ketone peroxide and2,4-dichlorobenzoyl peroxide, etc., can be used. These initiators can beused in combination to control the molecular weight and molecular weightdistribution of the resultant polymer. The addition amount of theinitiator is from 0.05 to 15 parts by weight, and more preferably from0.5 to 10 parts by weight, per 100 parts by weight of the monomer used.

[0116] In the condensation polymerization and addition polymerizationmentioned above, the resultant polymers have a non-linear structure or alinear structure depending on the monomer or monomers used. In thepresent invention, both a non-linear polymer (A) and a linear polymer(B) are used.

[0117] In the present invention, the non-linear polymer means a polymerhaving a crosslinked structure, and the linear polymer means a polymerhaving substantially no crosslinked structure. Polymers having acrosslinked structure can be prepared for example, by performingpolymerization using a monomer having three or more reactive groups.

[0118] In the present invention, in order to prepare the hybrid resin(C) in which a condensation-polymerized resin is chemically bonded withan addition-polymerized resin, it is preferable to performpolymerization in a container using monomers for thecondensation-polymerized resin and the addition-polymerized resin and adouble-reactive monomer which can react with the monomers for thecondensation-polymerized resin and the addition-polymerized resin.Specific examples of such double-reactive monomers include fumaric acid,acrylic acid, methacrylic acid, maleic acid, dimethyl fumarate, etc.

[0119] The addition amount of the double-reactive monomer is from 1 to25 parts by weight, and preferably from 2 to 10 parts by weight, per 100parts by weight of the monomers used. When the addition amount is lessthan 1 part by weight, the dispersion of the colorant and charge controlagent in the toner deteriorates, and thereby the image qualitiesdeteriorate (for example, background fouling occurs). When the additionamount is greater than 25 parts by weight, the resin tends to gelate.

[0120] When this polymerization is performed in a container, proceedingor completion of both reactions (i.e., condensation polymerizationreaction and addition polymerization reaction) can be performed at thesame time (i.e., parallel reaction). In addition, it is possible toindependently perform the reactions by properly setting the reactiontemperature and/or reaction time.

[0121] For example, the polymerization of the hybrid resin (C) isperformed as follows. A mixture of condensation-polymerizable monomersfor a polyester resin is contained in a container, and then a mixture ofaddition-polymerizable monomers for a vinyl resin and a polymerizationinitiator is added thereto drop by drop to firstly complete the radicalpolymerization reaction of the addition-polymerizable monomers for thevinyl resin. Then the temperature of the mixture is increased tocomplete the condensation polymerization reaction, resulting information of the polyester resin. By performing the two differentpolymerizations independently in a container, the two different resinscan be effectively dispersed.

[0122] In the toner of the present invention, a resin other than theabove-mentioned resins can be used as a binder resin in combination withthe above-mentioned resins in an addition amount such that the resindoes not deteriorate the toner properties. Specific examples of such aresin include the following, but are not limited thereto.

[0123] Polyurethane resins, silicone resins, ketone resins, petroleumresins, hydrogenated petroleum resins, etc. These resins can be usedalone or in combination. The method for manufacturing these resins isnot particularly limited, and any known polymerization methods such asbulk polymerization, solution polymerization, emulsion polymerization,and suspension polymerization can be used.

[0124] The salicylic acid metal compound for use in the presentinvention has the following formula (1):

[0125] wherein R1, R2, R3 and R4 independently represent a hydrogenatom, an alkyl group having 1 to 18 carbon atoms or an allyl group,wherein R1 and R2, R2 and R3, or R3 and R4 optionally share bondconnectivity to form an aromatic or aliphatic group optionally having asubstituent; M represents a metal; and m is an integer not less than 3and n is an integer not less than 2.

[0126] All metals can be used as the center metal M. Among the metals,Fe, Ni, Al, Ti, and Zr are preferable, and Fe is the most preferable inview of safety.

[0127] By using the above-mentioned resins (A), (B) and (C) and asalicylic metal compound, the offset resistance of the resultant tonercan be improved. When the center metal M has 2-valence or less, theoffset resistance cannot be improved.

[0128] The toner of the present invention can include a colorant, amagnetic material, a charge controlling agent, an additive, etc. ifdesired.

[0129] Specific examples of the colorant include known dyes and pigmentssuch as carbon black, lamp black, iron black, Aniline Blue,Phthalocyanine Blue, Phthalocyanine Green, Hansa Yellow G, Rhodamine 6CLake, chalco-oil blue, Chrome Yellow, quinacridone, Benzidine Yellow,Rose Bengale and triarylmethane. These dyes and pigments can be usedalone or in combination. The toner of the present invention can be usedas a black toner or a color toner. The content of the colorant in thetoner is from 1 to 30% by weight, and preferably from 3 to 20% byweight, based on total resin components in the toner.

[0130] By including a magnetic material in the toner of the presentinvention, the toner can be used as a magnetic toner. Specific examplesof the magnetic materials include iron oxides such as magnetite,hematite and ferrite; metals such as iron, cobalt and nickel; metalalloys of iron, cobalt or nickel with one or more of metals such asaluminum, copper, lead, magnesium, tin, zinc, antimony, beryllium,bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten andvanadium; mixture of these materials; etc.

[0131] When these ferromagnetic materials are included in the toner ofthe present invention, the average particle diameter thereof ispreferably from 0.1 to 2 μm. The content thereof in the toner is fromabout 20 to about 200 parts by weight, and preferably from 40 to 150parts by weight, per 100 parts by weight of total resin components inthe toner.

[0132] Suitable charge controlling agents for use in the toner of thepresent invention include known polarity controlling agents such asNigrosine dyes, metal complex dyes and quaternary ammonium salts. Thepolarity controlling agents can be used alone or in combination.Suitable negative charge controlling agents include metal complexes ofmonoazo dyes, salicylic acid and dicarboxylic acids. The content of suchpolarity controlling agents in the toner is from 0.1 to 10 parts byweight, and preferably from 1 to 5 parts by weight, per 100 parts byweight of the resin components in the toner.

[0133] In the toner of the present invention, known inorganic fillerscan be added as an external additive to the toner particles. It ispreferable to add at least two different inorganic fillers.

[0134] The external additive is preferably added such that the surfaceof toner particles are covered at a coverage not less than 20%. It isconsidered that by adding an external additive in such an amount, therelease agent present on the surface of a toner can be covered by theexternal additive to some extent, or a thin film of the release agentadhered on the surface of a photoreceptor or a developing sleeve can bescraped by the external additive. Thus, to add an external additiveassists in exerting the effects of the toner of the present invention.In the present invention, the coverage is measured as follows:

[0135] (1) the surface of a toner is observed with a field emissionscanning electron microscope (FE-SEM) and photographed;

[0136] (2) the image of the photograph is analyzed to determine theratio (i.e. the coverage) of a surface area of the toner particles onwhich the external additive adheres to the total surface area of thetoner particles in the photograph.

[0137] Specific examples of the inorganic fillers for use as theexternal additive include silica, alumina, titanium oxide, bariumtitanate, magnesium titanate, calcium titanate, strontium titanate, ironoxide, copper oxide, zinc oxide, tin oxide, silica sand, clay, mica,wollastonite, diatomite, chromiumoxide, ceriumoxide, redironoxide,antimonytrioxide, magnesium oxide, zirconium oxide, barium sulfate,barium carbonate, calciumcarbonate, siliconcarbide, siliconnitride, etc.In the present invention, it is preferable to use a combination of asilica with a titanium oxide as the external additive because theresultant toner has proper abrading ability, which is advantageous toprevent the filming problem, and the combination can impart good chargestability to the toner.

[0138] In the present invention, it is preferable to use two differentinorganic fillers having different average primary particle diameters.It is known that external additives are embedded into toner particleswhen stresses are applied thereto in a developing process. When twodifferent inorganic fillers having different particle diameters areused, the larger filler serves as a spacer when the toner particlescontact the surface of a photoreceptor and/or a toner carrier, andtherefore the smaller filler is prevented from being embedded into thetoner. Therefore, the initial surface conditions of the toner can bemaintained for a long period of time, resulting in maintenance of thefilming problem preventing effect.

[0139] When two different inorganic fillers are used, the inorganicfiller having a smaller average primary particle diameter should beadded in an amount greater than that of the inorganic filler having alarger average primary particle diameter. In this case, the propertiesof the resultant toner hardly change even when the toner is used for along period of time. This is because the larger filler tends to begradually embedded into the toner at first while the smaller fillerstays on the surface of the toner.

[0140] One of the two different inorganic fillers preferably has anaverage primary particle diameter not greater than 0.03 μm to impartgood fluidity to the resultant toner. When such a filler is added, theresultant toner has good fluidity, and therefore the toner can beuniformly charged, resulting in prevention of toner scattering andbackground fouling.

[0141] Another filler preferably has an average primary particlediameter not greater than 0.2 μm. As mentioned above, a filler having aparticle diameter not greater than 0.03 μm imparts good fluidity to theresultant toner. In this case, when a filler having a particle diameternot greater than 0.2 μm is used in combination, the fluidity is furtherenhanced, and thereby the toner is more uniformly charged.

[0142] At least one of the two different inorganic fillers is preferablya hydrophobized inorganic filler which is treated with an organic silanecompound because the resultant toner exhibits high stability towithstand environmental conditions, and in addition can produce highquality images without image defects such as omissions in characterimages. Needless to say, both the two different inorganic fillers may behydrophobized.

[0143] Specific examples of hydrophobizing agent include organic silanecompounds such as dimethyldichlorosilane, trimethylchlorosilane,methyltrichlorosilane, allyldimethyldichlorosilane,allylphenyldichlorosilane, benzyldimethylchlorosilane,bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane,p-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane,chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane,3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane,vinyltriethoxysilane, vinylmethoxysilane, vinyltris (β-methoxyethoxy)silane, γ-mehacryloxypropyltrimethoxysilane, vinyltriacetoxysilane,divinyldichlorosilane, dimethylvinylchlorosilane, octyltrichlorosilane,decyltrichlorosilane, nonyltrichlorosilane,(4-tert-propylphenyl)trichlorosilane, (4-tert-butylphenyl)trichlorosilane, dipentyldichlorosilane, dihexyldichlorosilane,dioctyldichlorosilane, dinonyldichlorosilane, didecyldichlorosilane,didodecyldichlorosilane, dihexadecyldichlorosilane, (4-tert-butylphenyl)octyldichlorosilane, dioctyldichlorosilane, didecenyldichlorosilane,dinonenyldichlorosilane, di-2-ethylhexyldichlorosilane,di-3,3-dimethylpentyldichlorosilane, trihexylchlorosilane,trioctylchlorosilane, tridecylchlorosilane, dioctylmethylchlorosilane,octyldimethylchlorosiolane, (4-tert-propylphenyl)diethylchlorosilane,isobutyltrimethoxysilane, methyltrimethoxysilane, octyltrimethoxysilane,trimethoxy(3,3,3-trifluoropropyl)silane, hexamethyldisilazane,hexaethyldisilazane, diethyltetramethyldisilazane, hexaphenyldisilazaneand hexatolyldisilazane; silicone oils such as dimethylsilicone oil,methylphenylsilicone oil, chlorophenylsilicone oil,methylhydrogensilicone oil, alkyl-modified silicone oils,fluorine-modified silicone oils, polyether-modified silicone oils,alcohol-modified silicone oils, amino-modified silicone oils,epoxy-modified silicone oils, epoxy/polyether-modified silicone oils,phenol-modified silicone oils, carboxyl-modified silicone oils,mercapto-modified silicone oils, acrylic-modified silicone oils,methacrylic-modified silicone oils, and α-methylstyrene-modifiedsilicone oils; silylation agents; silane coupling agents having an alkylfluoride group; organic titanate coupling agents; aluminum couplingagents; etc. Among these compounds, organic silane compounds arepreferably used.

[0144] By treating the inorganic fillers mentioned above with one ormore of these hydrophobizing agents, hydrophobic inorganic fillers foruse as an external additive of the toner of the present invention can beprepared.

[0145] Specific examples of the hydrophobized silica, which have beenmarketed, include HDK H 2000, HDK H 2000/4, HDK H 2050EP, and HVK21(which are manufactured by Hoechst AG); R932, R974, RX200, RY200, R202,R805, and R812 (which are manufactured by Nippon Aerosil Co.); and TS530and TS720 (which are manufactured by Cabot Corp).

[0146] Suitable titanium oxides for use as the hydrophobized titaniumoxide include crystalline titanium oxides having an anatase crystal formor a rutile crystal form or amorphous titanium oxides. Specific examplesof the hydrophobized titanium oxides, which have been marketed, includeT-805 (Nippon Aerosil Co.); MT150AI and MT150AFM (which has a rutilecrystal form and are manufactured by Tayca Corp.); STT-30A (rutilecrystal form) and STT-30A-FS (which are manufactured by Titan KogyoK.K.); etc.

[0147] The particle diameter of the inorganic fillers for use in thepresent toner is measured using a particle diameter distributionmeasuring instrument utilizing dynamic light scattering, such as DLS-700manufactured by Otsuka Electronics Co. Ltd. or Coulter N4 manufacturedby Coulter Electronics Inc. It is hard to dissociate an aggregatedorganic silane compound which has been subjected to a hydrophobizingtreatment. Therefore, it is preferable to measure the particle diameterof such a hydrophobized filler using a scanning electron microscopeoratransmissionelectronmicroscope. Inthis case, measurements should beperformed for at least 100 particles and the average value of the majordiameters should be determined.

[0148] In another aspect of the present invention, two-componentdeveloper including the toner of the present invention and a carrier isprovided. Suitable carriers for use in the present invention includeknown carriers. For example, magnetic powders such as iron powders,ferrite powders and nickel powders; glass beads; etc. can be used. Thesurface of such carrier materials may be treated with a resin, etc.

[0149] Suitable resins useful for coating carriers includestyrene-acrylic copolymers, silicone resins, maleic acid resins,fluorine-containing resins, polyester resins, epoxy resins, etc. Whenstyrene-acrylic copolymers are used, the fraction of styrene ispreferably from 30 to 90% by weight. When the fraction of styrene isless than 30% by weight, the resultant developer has poor developingproperties. In contrast, when the fraction is greater than 90% byweight, the coated film is hard and therefore tends to be easily peeledfrom the carrier material, resulting in shortening of life of thecarrier.

[0150] When a carrier is coated with a resin, additives such as adhesionimparting agents, hardeners, lubricants, electroconductive agents, andcharge controlling agents may be added to the resin.

[0151] Next, the image forming apparatus of the present invention willbe explained in detail.

[0152]FIG. 1 is a graph illustrating changes of the temperature of afixing member for use in the image forming apparatus of the presentinvention with lapse of time, and the changes of the electric powerconsumption of the image forming apparatus are illustrated in FIG. 2.

[0153] In general, when image forming operation is not performed (i.e.,in a no-operation period), the temperature of a fixing member is lowerthan that the fixing temperature to minimize the power consumption ofthe image forming apparatus. The temperature of the fixing element islowest just after electric power is applied to the image formingapparatus because pre-heating is not performed. Therefore, it is neededto wait for a period (a waiting period) until an image is printed out(i.e., until the temperature reaches the fixing temperature) Thetemperature of the fixing element changes as shown in FIG. 1. After theprinting operations are completed, power is not supplied to the fixingelement, and therefore the temperature of the fixing element graduallydecreases (i.e., the fixing device achieves a waiting state). When anorder to print out an image is made again, the cycle of waiting andprinting-out is repeated. The electric power consumption of the imageforming apparatus which is operated as shown in FIG. 1 is shown in FIG.2. The total power consumption is obtained by integrating electric powerconsumption with a time. It is effective for energy saving to shortenthe waiting period.

[0154] FIGS. 3-6 are schematic views illustrating the main parts ofembodiments of the fixing device of the image forming apparatus of thepresent invention.

[0155] The image forming method and apparatus of the present inventionwill be explained in detail referring to the drawings.

[0156] One of the fixing method in the image forming method of thepresent invention is to fix a toner image held on a support uponapplication of heat by passing the support through a nip between twofixing members which are heated. As the fixing members, rollers andfilms can be used. For example, the structure of a fixing device usingtwo rollers is shown in FIG. 3. In FIG. 3, numerals 10, 1 and 2 denote afixing device, a fixing roller and a pressure roller, respectively. Thefixing roller 1 has a metal cylinder 3 made of a good heat conductivematerial such as aluminum, iron, stainless steel or brass, and an offsetpreventing layer 4 which is formed on the surface of the metal cylinder3. The offset preventing layer 4 is typically made of a material such asRTV, silicone rubbers, tetrafluoroethyleneperfluoroalkylvinylether(PFA), or .polytetrafluoroethylene (PTFE).

[0157] A heat lamp 5 is arranged inside the metal cylinder 3. Thepressure roller 2 has a metal cylinder 6, which is typically made of thesame metal as that of the metal cylinder 3. On the surface of the metalcylinder 7, an offset preventing layer 7, which is made of a materialsuch as PFA and PTFE, is formed. Optionally, aheat lamp 8 is arrangedinside the pressure roller. The fixing roller 1 and the pressure roller2 rotate while being pressed to each other by springs (not shown)provided on both ends thereof. A support S, such as paper, having atoner image T is passed through a nip between the fixing roller 1 andthe pressure roller 2, and thereby the toner image T is fixed on thesupport.

[0158] In the fixing device for use in the present invention, the metalcylinder 3 of the fixing roller 1 has a thickness not greater than 0.7mm. By using such a metal cylinder, the temperature rising property ofthe fixing roller 1 can be improved, and the temperature of the fixingroller 1 can be rapidly raised to the predetermined temperature. Thethickness of the metal cylinder 3 is determined depending on themechanical strength and heat conductivity of the material used, butthickness is preferably from 0.2 to 5 mm. In addition, the pressure(surface pressure) applied between the fixing roller 1 and the pressureroller is preferable not less than 1.5×10⁵ Pa. The surface pressure isdefined as L/A, wherein L represents a load applied to the both ends ofthe two rollers and A represents a contact area of the two rollers. Thecontact area can be measured as follows:

[0159] (1) a sheet such as OHP (overhead projection) sheets, whichchanges its surface conditions upon application of heat, is passedthrough a nip between the two rollers heated;

[0160] (2) the sheet is suddenly stopped while being nipped by the tworollers;

[0161] (3) after the sheet is nipped for tens second, the sheetdischarged from the two rollers; and

[0162] (4) the area of the changed portion of the sheet is measured,which is the contact area.

[0163] To increase the surface pressure is advantageous for fixing tonerimages. However, when the surface pressure is increased in the fixingdevice in which the metal cylinders have a thickness not greater than0.7 mm, the roller tends to be deformed, resulting in occurrence ofproblems such as wrinkling and jamming of transfer sheets. Therefore, alarge pressure cannot be applied, and the pressure is preferably notgreater than 1.5×10⁵ Pa, and more preferably from 0.4 to 1.0×10⁵ Pa.

[0164] By using a fixing device having such a construction as mentionedabove, the toner image, which is made of the toner of the presentinvention having good high temperature preservability, can be fixed at alow temperature even when the waiting period is short. The presentinventors discover that the reasons why the toner of the presentinvention has good fixbility even when used for such a fixing devicehaving a low surface pressure are that the toner particles are embeddedinto a receiving paper (i.e., anchor effect), and in addition the tonerparticles are strongly bound with each other when heated due to highcohesive force of the toner particles. Thus, it is discovered that finetoner particles are preferable for preparing a strongly fixed tonerimage.

[0165]FIG. 4 illustrates an embodiment of the fixing device having oneheating member for use in the present invention.

[0166] In the fixing device as shown. in FIG. 4, a belt heating member31 serves as the heating member. The belt heating member 31 is pressedby a pressing member 33 toward a fixed heater 32. In addition, the beltheating member 31 is tightened by tension applying members 34. Arecording material 28 is passed through a contact heating region 35formed by the belt heating member 31 and the pressing member 33, by afeeding member (not shown) A toner image on the recording material isfixed at the contact heating region 35 upon application of heat andpressure. At this point, the toner image is formed on the side of therecording material 28 contacting the belt heating member 31.

[0167]FIG. 5 illustrates another embodiment of the fixing device havingtwo heating members for use in the present invention. In this case, acontact heating region is mainly formed by the pressure of a pressingmember.

[0168] A fixing device 40 has a hollowcylinder-shaped heating member 41and a belt-shaped heating member 42 as the heating members. Inside thecylinder heating member 41, a heater 43 is arranged. The belt heatingmember 42 is pressed by a pressing member 44 toward the roller heatingmember 41. In addition, the belt heating member 42 is tightened byrotatable roller-shaped tension applying member 45. A recording material28 is fed by a feeding member (notshown) toward a contact heating region46 formed between the belt heating member 42 and the pressing member 44.A toner image on the recording material 28 is fixed at the contactheating region 46 upon application of heat and pressure. At this point,the toner image is formed on the side of the recording material 28contacting the belt heating member 42.

[0169]FIG. 6 illustrates another embodiment of the fixing device havingtwo heating members for use in the present invention. In this case, acontact heating region is mainly formed by the tension of a belt heatingmember.

[0170] A fixing device 50 has a hollow-cylinder-shaped heating member 51and a belt-shaped heating member 52 as the heating members. Inside theroller heating member 51, a heater 53 is arranged. The belt heatingmember 52 is tightened by a rotatable roller-shaped tension applyingmember 54 and pressed by a pressing member 55 to form a contact heatingregion 56. A recording material 28 is fed by a feeding member (notshown) toward the contact heating region 56 formed between the beltheating member 52 and the pressing member 55. A toner image on therecording material 28 is fixed at the contact heating region 56 uponapplication of heat and pressure. At this point, the toner image isformed on the side of the recording material 28 contacting the beltheating member 52.

[0171] In addition, these fixing devices may have a release agentapplying mechanism which applies a release oil on the heating members toavoid or assist in avoiding the offset problem.

[0172] In the image forming apparatus of the present invention, thewaiting period (i.e., a time from powering-up to a time when an imageforming operation can be started) not longer than 15 seconds, andpreferably not longer than 10 seconds. In addition, the total powerconsumption when image forming operations are performed is not greaterthan 1.5 KW, and the total power consumption when image formingoperations are not performed is not greater than 30 W. In particular,when the toner of the present invention is used for an image formingapparatus capable of producing 30 or more A-4 size copy sheets per 1minute, the toner images can be fixed at a low temperature and therebythe total power consumption can be reduced.

[0173] In other aspects of the present invention, a toner containercontaining the toner of the present invention; an image formingapparatus having the toner container; a developer container containing atwo-component developer including the toner of the present invention anda carrier; and an image forming apparatus having the developer containerare provided.

[0174] Next, the developing device for use in the present invention willbe explained.

[0175]FIG. 7 is a schematic view illustrating the developing section ofan embodiment of the image forming apparatus of the present invention.

[0176] A developing device 13 arranged beside a photoreceptor drum 11includes a case 14, a developing sleeve serving as a developer bearingmember, a developer containing member 16, a first doctor blade 17serving as a developer regulating member.

[0177] The case 14 has an opening facing the photoreceptor drum 11, anda toner hopper 19 serving as a toner containing member and containing atoner 18 therein is formed in the case 14. At a position of the tonerhopper 19 near the photoreceptor drum 11, a developer containing member16, in which a developer containing portion 16 a containing a developer22 including the toner 18 and a magnetic carrier is formed, is arrangedwhile integrated with the case 14. At a position of the case 14 belowthe developer containing member 16, a projection 14 a having an opposingface 14 b is formed. In addition, a toner supplying opening 20 fromwhich the toner 18 is fed is formed between the lower part of thedeveloper containingmember 16 and the opposing face 14 b.

[0178] Inside of the toner hopper 19, a toner agitator 21 which isrotated by a driving device (not shown) and which serves as a tonersupplier is arranged. The toner agitator 21 feeds the toner 18 in thetoner hopper 19 toward the toner supplying opening 20 while, agitatingthe toner 18. In addition, a toner end detecting device 14 c whichdetects that the amount of toner 18 present in the toner hopper 19 issmall is arranged.

[0179] At a space between the photoreceptor drum 11 and the toner hopper19, the developing sleeve 15 is arranged. The developing sleeve 15 isrotated by a driving member (not shown) in a direction indicated by anarrow. Inside the developing sleeve, a magnet (not shown) which servesas a magnetic field generating member is arranged while the position ofthe magnet is fixed relative to the developing device 13. At a positionof the side of the developer containing member 16 opposite to the sideat which the developer containing member 16 is connected with the case14, the first doctor blade 17 is arranged while integrated with thedeveloper containing member 16. The first doctor blade 17 is arrangedsuch that a gap is formed between the tip edge thereof and the peripherysurface of the developing sleeve 15.

[0180] At a position of the developer containing member 16 near thetoner supplying opening 20, a second doctor blade 23 serving as aregulating member is arranged. The second doctor blade 23 is fixed onthe developer containing member 16 such that a space is formed betweenthe tip edge (i.e., the free edge) of the second doctor blade 23 and theperiphery surface of the developing sleeve 15 and the tip edge isdirected toward the center of the developing sleeve, to regulate theflow of the developer layer.

[0181] The developer containing portion 16 a has a space sufficient tomove the developer 22 within the magnetic filed of the developing sleevewhile the developer 22 is circulated therein.

[0182] The opposing face 14 b has a predetermined length and is formedso as to be slanted downwardly from the toner hopper side toward thedeveloping sleeve side. By taking such construction, even when thecarrier in the developer containing portion 16 a is dropped from thespace formed between the second doctor blade 23 and the developingsleeve 15 due to vibration of the developing device, uneven magneticfield of the magnet inside the developing sleeve 15 and/or partialincrease of toner concentration of the developer 22, the dropped carrieris received by the opposing face 14 b and moves toward the developingsleeve 16. Then the carrier is born on the surface of the developingsleeve 15 by the magnetic force of the magnet and fed again to thedeveloper containing portion 16 a. Thus, decrease of amount of thecarrier in the developer containing portion 16 a can be prevented.Therefore, a problem in that an image having an uneven image density inthe direction of the axis of the developing sleeve 15 is produced can beavoided. The opposing face 14 a has a slanting angle of about 5°, and alength l of from 2 to 20 mm and preferably from 3 to 10 mm.

[0183] The toner 18 fed from the toner hopper 19 by the toner agitator21 is supplied to the developer 22 born by the developing sleeve 15after passing through the toner supplying opening 20. Then the toner 18is fed to the developer containing portion 16 a. The developer 22 in thedeveloper containing portion 16 a is born on the developing sleeve 15and fed to a developing position at which the developing sleeve 15 facesthe periphery surface of the photoreceptor drum 11. At the developingposition, the toner in the developer layer is attracted by anelectrostatic latent image formed on the photoreceptor drum 11,resulting in formation of a toner image on the photoreceptor 11.

[0184] In FIG. 7, numerals 100 and 101 denote a toner containercontaining a toner and a developer container containing a developer(i.e. a toner and a carrier). In addition, numeral 12 denotes an imagetransferer which transfers a toner image on the photoreceptor drum 11 toa receiving material 28. In this case, the toner image is transferred ona receivingmaterial via an intermediate transfer medium (not shown).

[0185] The behavior of the developer 22 when the toner image is formedwill be explained. When a start developer consisting of only a carrier22 a is set in the developing device 13, the carrier 22 a is separatedinto two groups, one of which is adhered on the surface of thedeveloping sleeve 15 and the other of which is contained in thedeveloper containing portion 16 a, as shown in FIG. 8.

[0186] The carrier 22 a in the developer containing portion. 16 a iscirculated in a direction indicated by an arrow b at a speed not lessthan 1 mm/s due to the magnetic force of the magnet. This circulation iscaused by the rotation of the developing sleeve 15 in a directionindicated by an arrow a. An interface X is formed between the surface ofthe carrier born on the surface of the developing sleeve 15 and thesurface of the carrier 22 a circulated in the developer containingportion 16 a.

[0187] Then the toner 18 is contained in the toner hopper 19. When thetoner 18 is set, the toner 18 is fed to the magnetic carrier 22 a bornon the developing sleeve 15 from the toner supplying opening 20.Therefore the developing sleeve 15 bears. the developer 22 which is amixture of the toner 18 and the carrier 22 a.

[0188] In the developer containing portion 16 a, a force is appliedagainst the developer 22 fed by the developing sleeve 15 such that themovement of the developer 22 is stopped because another group of thedeveloper 22 is present in the developer containing portion 16 a. Whenthe toner present on the surface of the developer 22 born on the surfaceof the developing sleeve 15 is fed to the interface X, the friction ofthe developer 22 near the interface X decreases, resulting in decreaseof the feeding ability of the developer 22 near the interface X, andthereby the amount of the fed developer 22 neat the interface X isdecreased.

[0189] On the other hand, the developer present on the developing sleeve15 on the upstream side from a junction Y relative to the rotatingdirection of the developing sleeve 15 does not receive the force whichis applied to the developer 22 fed to the developer containing portion16 a as mentioned above. Therefore, the amount of the developer 22 fedto the junction Y is unbalanced with the amount of the developer 22 fedin the region of the interface X, resulting in collision of thedeveloper 22. Therefore, the position of the junction Y is heightened,i.e., the layer of the developer 22 including the interface X thickensas shown in FIG. 9. In addition, the layer of the developer formed at aposition after the first doctor blade 17 also thickens gradually asshown in FIG. 9. The thickened developer layer is scraped by the seconddoctor blade 23.

[0190] When the toner concentration of the developer 22 passed the firstdoctor blade 17 reaches a predetermined toner concentration, thedeveloper 22, which is scraped by the second doctor blade 23 andlayered, covers the toner supplying opening 20, and thereby the feedingof the toner 18 is stopped, as shown in FIG. 10. At this point, thevolume of the developer 22 increases in the developer containing portion16 a because the toner concentration thereof increases. Thereby, thefree space in the developer containing portion 16 a is decreased, andthe speed of the circulation of the developer 22 in the directionindicated by the arrow b is decreased.

[0191] The layer of the developer 22 covering the toner supplyingopening 20 is scraped by the second doctor blade 23. As shown by anarrow c in FIG. 10, the scraped developer moves at a speed not less than1 mm/s and is received by the opposing face 14 b. Since the opposingface 14 b is slanted downwardly at an angle of α and has a length L, thedeveloper 22 is prevented from dropping in the toner hopper 19, andthereby the amount of the developer 22 is maintained so as to beuniform. Therefore the toner supply can be self-controlled.

[0192] Having generally described this invention, further understandingcan be obtained by reference to certain specific examples which areprovided herein for the purpose of illustration only and are notintended to be limiting. In the descriptions in the following examples,the numbers represent weight ratios in parts, unless otherwisespecified.

EXAMPLES Resin Manufacturing Example

[0193] Manufacturing of Non-linear Polyester Resin (A)

[0194] Ten (10) moles of fumaric acid, 4 moles of trimellitic acid, 6moles of bisphenol A-(2,2)propylene oxide and 4 moles of bisphenolA-(2,2)ethylene oxide were contained in a flask having a stainless steelagitator, a condenser, a nitrogen gas leading tube and a thermometer.The mixture was heated to 220° C. under a nitrogen gas flow while beingagitated, to perform a condensation polymerization reaction. Thus anon-linear polyester resin was prepared.

[0195] Manufacturing of Linear Polyester Resin (B)

[0196] Eight (8) moles of terephthalic acid, 6 moles of bisphenolA-(2,2)propylene oxide and 4 moles of bisphenol A-(2,2)ethylene oxidewere contained in a flask having a stainless steel agitator, acondenser, anitrogen gas leading tube and a thermometer. The mixture washeated to 220° C. under a nitrogen gas flow while being agitated, toperform a condensation polymerization reaction. Thus a linear polyesterresin was prepared.

[0197] Manufacturing of Hybrid Resin (C)

[0198] Twenty (20) moles of styrene and 5 moles of butyl methacrylate,which serve as addition polymerization monomers and 0.4 moles oft-butylhydroperoxide serving as a polymerization initiator werecontained in a dropping funnel. On the other hand, 10 moles of fumaricacid serving as a double-reactive monomer capable ofaddition-polymerizing and condensation-polymerizing, 4 moles oftrimellitic anhydride, 6 moles of bisphenol A-(2,2)propylene oxide and 4moles of bisphenol A-(2,2)ethylene oxide, which arecondensation-polymerizable monomers, and 60 moles of dibutyltinoxideserving as an esterifying agent were contained in a flask having astainless steel agitator, a condenser, a nitrogen gas leading tube and athermometer. The mixture was heated to 135° C. under a nitrogen gas flowwhile being agitated.

[0199] The above-prepared mixture for addition polymerization wasdropped into the flask from the dropping funnel while spending 5 hours.After dropping was completed, the mixture in the flask was aged at 135°C. for 6 hours. Then the mixture was heated to 220° C. to perform areaction. Thus a hybrid resin was prepared.

[0200] The above-mentioned polymerization of each of the polymers A, Band C was performed while the polymerization degree of each polymer waschecked by a method in which the softening point of the reaction productwas measured by a method based on ASTM E28-67. When the reaction producthad predetermined softening point, the polymerization reaction wasstopped. Then the reaction product was pulled out of the flask, andpulverized after being cooled. Thus a polymer having predeterminedproperties was prepared.

[0201] Manufacturing of Carrier

[0202] The following components were mixed for 20 minutes using ahomomixer to prepare a coating liquid. Silicone resin (organo straightsilicone) 100 Toluene 100 γ-(2-aminoethyl)aminopropyltrimethoxysilane 5Carbon black 10

[0203] Then 1000 parts of a particulate magnetite having a sphericalshape and a particle diameter of 50 μm were coated with the coatingliquid using a fluidized bed type coating apparatus. Thus a magneticcarrier A was prepared.

Example 1

[0204] The following components were mixed in a Henshel mixer.Non-linear polyester resin (A) 60 (acid value of 16.3 mgKOH/g, hydroxylvalue of 35.1 mgKOH/g, softening point of 145.1° C., and glasstransition temperature of 61.5° C.) Linear polyester resin (B) 40 (acidvalue of 2.1 mgKOH/g, hydroxyl value of 34 mgKOH/g, softening point of100.8° C., and glass transition temperature of 60.3° C.) Carnauba wax4.5 (particle diameter of 400 μm) Carbon black 8 (#44 from MitsubishiKasei Corp.) Zn (II) complex of 3,5-di-tert-butylsalicylic acid 3

[0205] The mixture was heated to 130° C. and kneaded for about 30minutes. The kneaded mixture was cooled to room temperature, and thencrushed with a hammer mill to prepare particles having a particlediameter of from 200 to 400 μm. The thus prepared particles werepulverized and classified using a pulverization/classification apparatusIDS-2 (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) in which apulverizer, in which the particles were collided with a plate using jetair to be pulverized, and a classifier, in which the pulverizedparticles were circulated in a room to be classified using centrifugalforce, are integrated. Thus toner particles were prepared. The particlediameter distribution of the toner particles was measured with a Coultercounter. The result is shown in Table 1.

[0206] Then 100 parts of the toner particles, and 0.6 parts of ahydrophobic silica R972 treated with a dichlorodimethylsilane(manufactured by Nippon Aerosil Co., and having an average primaryparticle diameter of 0.016 μm) and 0.2 parts of hydrophobic titaniumoxide T805 treated with octyltrimethoxysilane (manufactured by NipponAerosil Co., and having an average particle diameter of 0.02 μm), whichserve as external additives, were mixed using a Henshel mixer. Thus atoner was prepared.

[0207] Then 4 parts of the toner were mixed with 96 parts of theabove-prepared carrier to prepare a developer 1. The developer 1 wasevaluated by the methods mentioned below.

[0208] Measurements of Coefficient of Static Friction Three (3) grams ofthe thus prepared toner was included in a pellet forming die and pressedfor 1 minute upon application of load of 6 tons to form a plate-shapedtoner pellet having a diameter of 40 mm. The coefficient of staticfriction of the surface of the pellet was measured with theabove-mentioned automatic friction/abrasion analyzer (DFPM-SSmanufactured by Kyowa Interface Science Co., Ltd.) using a point contactmethod. The measuring conditions are as follows:

[0209] (1) Contact member: stainless steel ball

[0210] (2) Load: 50 g

[0211] (3) Stroke: 10 mm

[0212] The softening point of the resins used was measured by a methodbased on JIS K72101 using a flow tester (manufactured by ShimadzuCorp.). The measuring method is as follows:

[0213] (1) 1 cm³ of a resin sample is set in a cell and pressed by apressure of 20 Kg/cm² while being heated at a temperature rising speedof 6° C./min to extrude the resin sample from a nozzle of 1 mm indiameter and 1 mm in length:

[0214] (2) graphing the relationship between temperature and the amountof drop of the plunger; and

[0215] (3) provided that the height of the thus prepared S-shaped curveis h, the softening point of the resin is defined as the temperaturecorresponding to the point of h/2 on the curve (i.e., the temperature atwhich half of the resin sample flows away).

[0216] The acid value and hydroxyl value of resins are measured bymethods based on JIS K0070.

[0217] The glass transition temperature of resins are measured using adifferential scanning colorimeter DSC-60 manufactured by Shimadzu Corp.The measuring method is as follows:

[0218] (1) a resin sample is heated from room temperature to 200° C. ata temperature rising speed of 10° C./min, and then cooled at atemperature falling speed of 10° C./min; and

[0219] (2) the glass transition temperature (Tg) is defined as thetemperature corresponding to a middle point of the base line 1 in whichthe temperature is below the Tg and the base line 2 in which thetemperature is above the Tg.

Examples 2, 3 and 4

[0220] The procedures for preparation and evaluation of the toner anddeveloper in Example 1 were repeated except that the particle diameterdistribution of the toner particles was changed as described in Table 1by changing the amount of the particles supplied to thepulverization/classification apparatus and the pulverizing air pressure.

Example 5

[0221] The procedures for preparation and evaluation of the toner anddeveloper in Example 1 were repeated except that the carnauba wax wasreplaced with a rice wax (particle diameter of 500 μm) when the tonerwas prepared.

Example 6

[0222] The procedures for preparation and evaluation of the toner anddeveloper in Example 1 were repeated except that the addition amount ofthe carnauba wax was changed to 3 parts.

Example 7

[0223] The procedures for preparation and evaluation of the toner andthe developer in Example 1 were repeated except that the temperature ofthe roll mill was changed 100° C. in the kneading process.

Example 8

[0224] The following components were mixed using a Henshel mixer.Non-linear polyester resin (A) 40 (acid value of 27.5 mgKOH/g, hydroxylvalue of 37.5 mgKOH/g, softening point of 148.5° C., and glasstransition temperature of 60° C.) Linear polyester resin (B) 60 (acidvalue of 10.1 mgKOH/g, hydroxyl value of 46.8 mgKOH/g, softening pointof 98.8° C., and glass transition temperature of 60.5° C.) Carnauba wax4.5 (particle diameter of 400 μm) Carbon black 8 (#44 from MitsubishiKasei Corp.) Fe(III) complex of 3,5-di-tert-butylsalicylic acid 3

[0225] The mixture was heated to 130° C. and kneaded for 30 minutesusing a roll mill. The kneaded mixture was cooled to room temperature,and then crushed with a hammer mill to prepare particles having aparticle diameter of from 200 to 400 μm. The thus prepared particleswere pulverized and classified using a pulverization/classificationapparatus IDS-2 (manufactured by Nippon Pneumatic Mfg. Co., Ltd.). Thustoner particles were prepared.

[0226] Then 100 parts of the toner particles, and 0.6 parts of ahydrophobic silica R972 treated with a dichlorodimethylsilane(manufactured by Nippon Aerosil Co., and having an average primaryparticle diameter of 0.016 μm) and 0.2 parts of hydrophobic titaniumoxide T805 treated with octyltrimethoxysilane (manufactured by NipponAerosil Co., and having an average particle diameter of 0.02 μm), whichserve as external additives, were mixed using a Henshel mixer. Thus atoner was prepared.

[0227] Then 4 parts of this toner were mixed with 96 parts of thecarrier A using a ball mill. Thus, a two component developer 8 wasprepared.

Example 9

[0228] The procedures for preparation and evaluation of the toner andthe developer in Example 8 were repeated except that the tonerconstituents were changed as follows: Non-linear polyester resin (A) 34Linear polyester resin (B) 54 Hybrid resin (C) 15 (acid value of 24.5mgKOH/g, hydroxyl value of 25.1 mgKOH/g, softening point of 113.5° C.,and glass transition temperature of 59.5° C.)

Comparative Example 1

[0229] The procedures for preparation and evaluation of the toner andthe developer in Example 1 were repeated except that the particlediameter of the carnauba wax was changed to 2 mm and the addition amountof the carnauba wax was changed to 20 parts. The friction coefficient ofthe surface of the toner was 0.14.

Comparative Example 2

[0230] The procedures for preparation and evaluation of the toner andthe developer in Example 1 were repeated except that the temperature ofthe roll mill in the kneading process was changed to 160° C. Thefriction coefficient of the surface of the toner was 0.18.

Comparative Example 3

[0231] The procedures for preparation and evaluation of the toner andthe developer in Example 1 were repeated except that the addition amountof the hydrophobic silica was changed to 0.3% and the hydrophobictitanium oxide was not added. The friction coefficient of the surface ofthe toner was 0.19.

Comparative Example 4

[0232] The procedures for preparation and evaluation of the toner andthe developer in Example 1 were repeated except that the addition amountof the carnauba wax was changed to 1.5% and the addition amounts of thehydrophobic silica and the hydrophobic titanium oxide were changed to2.0% and 1.0%, respectively. The friction coefficient of the surface ofthe toner was 0.45.

[0233] The thus prepared toners and developers were evaluated asfollows.

[0234] 1. Filming

[0235] Each of the toners and its developer were set in afilming-evaluating copying machine, a modified IMAGIO MF-200manufactured by Ricoh Co., Ltd. whose developing unit was modified, toperform a running test in which 100,000 copies are produced at roomtemperature. At the 20,000^(th) image, 50,000^(th) image and100,000^(th) image, the image was observed to determine whether thetoner was filmed on the photoreceptor and whether the image had anabnormal image (i.e., a white stripe image in half tone images).

[0236] Whether the film was formed on the photoreceptor can be judged bythe following method.

[0237] Copy papers of A-3 size, which had been stored for 2 hours underthe environmental conditions of 30° C. and 90% RH, were set in thecopying machine. Half tone images formed of 1 dot image (1 dot×1 dot)were output. The image densities of the darkest area and the lightestarea of the stripe images were measured with a Macbeth densitometer todetermine the difference of the image densities. The filming wasevaluated by being classified into the following 5 grades.

[0238] ⊚: the density difference is not greater than 0.05. (excellent)

[0239] ◯: the density difference is from 0.06 to 0.10.

[0240] □: the density difference is from 0.11 to 0.25.

[0241] Δ: the density difference is from 0.26 to 0.40.

[0242] X: the density difference is not less than 0.41. (worst)

[0243] When the film was not formed, the difference of image densitiesis 0.00. The larger the density difference, the worse the filmingphenomenon. In addition, the greater the number of copied images, theworse the filming phenomenon.

[0244]2. Reproducibility of Fine Lines

[0245] A line image including vertical and horizontal lines havingdensities of 2.0, 2.2, 2.5, 2.8, 3.2, 3.6, 4.0, 4.5, 5.0, 5.6, 6.3 and7.1 lines/mm was produced using a copier IMAGIO MF-200 manufactured byRicoh Co., Ltd. The line image was observed whether the line images canbe faithfully reproduced. The fine-line reproducibility of the image wasclassified into the following 5 grades.

[0246] ⊚: the lines having a density of from 6.3 to 7.1 lines/mm can bereproduced. (excellent)

[0247] ◯: the lines having a density of from 5.0 to 5.6 lines/mm can bereproduced.

[0248] □: the lines having a density of from 4.0 to 4.5 lines/mm can bereproduced.

[0249] Δ: the lines having a density of from 2.8 to 3.6 lines/mm can bereproduced.

[0250] X: the lines having a density of from 2.0 to 2.5 lines/mm can bereproduced. (worst)

[0251]3. Fixability

[0252] The fixability of each toner was evaluated using a copier, RicohIMAGIO MF-200 having a modified fixing section in which a Teflon rollerwas used as a fixing roller, and a TYPE 6200 copy paper manufactured byRicoh Co., Ltd. Images were produced while the fixing temperature waschanged. The image forming conditions of the copier for checking coldand hot offset problems were as follows.

[0253] Cold Offset

[0254] Paper feeding speed: 140 mm/s

[0255] Surface pressure of the fixing roller: 1.2 Kgf/cm²

[0256] Nip width of the fixing area: 3 mm

[0257] Hot Offset

[0258] Paper feeding speed: 50 mm/s

[0259] Surface pressure of the fixing roller: 2.0 Kgf/cm²

[0260] Nip width of the fixing area: 4.5 mm

[0261] The cold offset resistance and hot offset resistance of thetoners were classified into the following 5 grades.

[0262] Cold Offset Resistance

[0263] ⊚: cold offset is observed at a temperature not higher than 125°C. (excellent)

[0264]603 : cold offset is observed at a temperature not lower than 125°C. and not higher than 135° C.

[0265] □: cold offset is observed at a temperature not lower than 135°C. and not higher than 145° C.

[0266] Δ: cold offset is observed at a temperature not lower than 145°C. and not higher than 155° C.

[0267] X: cold offset is observed at a temperature not lower than 155°C. (worst)

[0268] Hot Offset Resistance

[0269] ⊚: hot offset is observed at a temperature not lower than 201° C.(excellent)

[0270]603 : hot offset is observed at a temperature of from 191° C. to200° C.

[0271] □: hot offset is observed at a temperature of from 181° C. to190° C.

[0272] Δ: hot offset is observed at a temperature of from 171° C. to180° C.

[0273] X: hot offset is observed at a temperature not higher than 170°C. (worst)

[0274] 4. High Temperature Preservability

[0275] Twenty (20) grams of a toner sample was contained in a glasscontainer having a volume of 20 ml. The glass container including thetoner was allowed to settle in an oven of 60° C. for 4 hours. Then thetoner was cooled and subjected to a penetration test by a method basedon JIS K2235-1991.

[0276] The high temperature preservability is classified into thefollowing 4 grades:

[0277] ⊚: penetration is not less than 10 mm. (excellent)

[0278] ◯: penetration is from 5.0 to 9.9 mm.

[0279] Δ: penetration is from 3.0 to 4.9 mm.

[0280] X: penetration is from 0 to 2.9 mm. (worst)

[0281]5. Background Fouling

[0282] A white image of A-3 size was formed after the 100,000 sheetsrunning test mentioned above. The average image density of the whiteimage was determined by measuring the densities of six points of thewhite image. Then the density difference between the average imagedensity of the white image and the image density of the paper which didnot pass the copy machine was determined. The density difference wasclassified into the following 5 grades to evaluate background fouling.

[0283] ⊚: the density difference is not greater than 0.02. (excellent)

[0284] ◯: the density difference is from 0.03 to 0.05.

[0285] □: the density difference is from 0.06 to 0.08.

[0286] Δ: the density difference is from 0.09 to 0.11.

[0287] X: the density difference is not less than 0.12. (worst) TABLE 1Filming P At At At D4 (% by 20,000^(th) 50,000^(th) 100,000^(th) μ0 (μm)number) image image image Ex. 1 0.26 9.5 25 ⊚ ⊚ ◯ Ex. 2 0.27 6.5 62 ⊚ ⊚◯ Ex. 3 0.28 7.7 60 ⊚ ⊚ ◯ Ex. 4 0.21 4.8 81 ⊚ ◯ ◯ Ex. 5 0.23 9.6 24 ⊚ ⊚◯ Ex. 6 0.39 9.4 27 ⊚ ⊚ ⊚ Ex. 7 0.29 9.5 25 ⊚ ⊚ ◯ Ex. 8 0.28 6.7 63 ⊚ ⊚◯ Ex. 9 0.33 6.6 62 ⊚ ⊚ ⊚ Comp. 0.14 9.5 25 X — — Ex. 1 Comp. 0.18 9.625 □ X — Ex. 2 Comp. 0.19 9.5 26 ◯ Δ X Ex. 3 Comp. 0.45 9.5 24 ⊚ ⊚ ⊚ Ex.4

[0288] μo: Coefficient of static friction of the surface of the toner

[0289] D4: Volume average particle diameter of the toner particles

[0290] P: Percentage of toner particles having a particle diameter notgreater than 5 μm Fine line Cold Back- reprod- offset Hot offset Pre-ground ucibility resistance resistance servability fouling Ex. 1 ◯ ◯ ◯ ◯◯ Ex. 2 ⊚ ◯ ◯ ◯ ◯ Ex. 3 ⊚-◯ ◯ ◯ ◯ ◯ Ex. 4 ⊚ ◯ ◯ ◯ ◯ Ex. 5 ◯ ◯ ◯ ◯ ◯ Ex.6 ◯ ◯ ◯ ◯ ◯ Ex. 7 ◯ ◯ ◯ ◯ ◯ Ex. 8 ⊚ ⊚ ⊚ ◯ ◯ Ex. 9 ⊚ ⊚ ⊚ ⊚ ◯ Comp. Ex. 1□ ◯ ⊚ X Δ Comp. Ex. 2 ◯ ◯ ◯ Δ □ Comp. Ex. 3 Δ ◯ ◯ Δ Δ Comp. Ex. 4 ◯ ◯ X◯ ◯

[0291] As can be understood from Table 1, by using the toner of thepresent invention, and image forming method and apparatus using thetoner, good images can be produced for a long period of time withoutcausing the offset and filming problems even when mechanical and thermalstresses are applied thereto.

[0292] This document claims priority and contains subject matter relatedto Japanese Patent Applications No. 2000-298734, 2000-324957,2001-026396 and 2001-233944, filed on Sep. 29, 2000, Oct. 25, 2000, Feb.2, 2001 and Aug. 1, 2001, respectively, incorporated herein byreference.

[0293] Having now fully described the invention, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made thereto without departing from the spirit and scope of theinvention as set forth therein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A toner composition comprising toner particles,said particles comprising a binder resin and a release agent, whereinwhen the toner composition is pressed upon application of a pressure of478 kg/cm² to form a toner plate, the toner plate has a surface having acoefficient of static friction of from 0.20 to 0.40.
 2. The tonercomposition according to claim 1, wherein the toner particles have avolume average particle diameter of from 4.0 to 7.5 μm and includesparticles having a particle diameter not greater than 5 μm in an amountof from 60 to 80% by number.
 3. The toner composition according to claim1, wherein the release agent comprises a material selected from thegroup consisting of carnauba waxes, montan waxes and oxidized ricewaxes.
 4. The toner composition according to claim 1, wherein therelease agent is present in the toner particles in an amount of from 2to 10% by weight based on the binder resin in the toner particles. 5.The toner composition according to claim 1, wherein the binder resincomprises a non-linear polymer A, a linear polymer B and a polymer C,wherein the polymer C is prepared by at least one of performing acondensation polymerization reaction and an addition polymerizationreaction at a same time in a container using a mixture of monomers forthe condensation polymerization reaction and the addition polymerizationreaction; and performing a condensation polymerization reaction and anaddition polymerization reaction independently in a container using amixture of monomers for the condensation polymerization reaction and theaddition polymerization reaction, and wherein the non-linear polymer A,the linear polymer B and the polymer C comprise a polymer unit of thesame kind.
 6. The toner composition according to claim 5, wherein thepolymer unit is a unit selected from the group consisting of polyesterunits and polyamide units.
 7. The toner composition according to claim5, wherein the following relationships are satisfied:Tm(A)>T(C)>Tm(B)|Tg(A)−Tg(B)|<10(° C.)30≦Tm(A)−Tm(B)≦60(° C.) whereinTm(A), Tm(B) and Tm(C) represent softening points of the non-linearpolymer A, the linear polymer B and the polymer C, respectively; andTg(A) and Tg(B) represent glass transition temperatures of thenon-linear polymer A and the linear polymer B, respectively.
 8. Thetoner composition according to claim 5, wherein the non-linear polymer Ahas an acid value of from 20 to 70 mgKOH/g.
 9. The toner compositionaccording to claim 5, wherein the linear polymer B has an acid value offrom 7 to 70 mgKOH/g.
 10. The toner composition according to claim 1,wherein the toner particles further comprises a salicylic acid metalcompound having at least 3 valence.
 11. The toner composition accordingto claim 10, wherein the salicylic acid metal compound is included inthe toner particles in an amount of from 0.05 to 10 parts by weight per100 parts by weight of the binder resin.
 12. The toner compositionaccording to claim 5, wherein the non-linear polymer A has a hydroxylvalue not less than 20 mgKOH/g.
 13. The toner composition according toclaim 1, further comprising an external additive, wherein the tonerparticles are covered by the external additive at a coverage not lessthan 20%.
 14. The toner composition according composition to claim 13,wherein the external additive comprises two different inorganic fillersA and B.
 15. The toner composition according to claim 14, wherein thetwo different inorganic fillers A and B are a silica and a titaniumoxide.
 16. The toner composition according to claim 14, wherein the twodifferent inorganic fillers A and B have different average primaryparticle diameters.
 17. The toner composition according to claim 16,wherein the inorganic filler A has an average primary particle diametersmaller than that of the inorganic filler B and is included in the tonercomposition in an amount greater than that of the inorganic filler B.18. The toner composition according to claim 16, wherein the inorganicfillers A and B have an average primary particle diameter not greaterthan 0.03 μm and not greater than 0.2 μm, respectively.
 19. The tonercomposition according to claim 14, wherein at least one of the inorganicfillers A and B is treated with an organic silane compound.
 20. A methodfor manufacturing a toner composition comprising: providing a polymer Cby at least one of performing a condensation polymerization reaction andan addition polymerization reaction at a same time in a container usinga mixture of monomers for the condensation polymerization reaction andaddition polymerization reaction; and performing a condensationpolymerization reaction and an addition polymerization reactionindependently in a container using a mixture of monomers for thecondensation polymerization reaction and addition polymerizationreaction; kneading a mixture comprising the polymer C, a non-linearpolymer A, a linear polymer B and a release agent upon application ofheat; cooling the mixture to solidify the mixture; pulverizing themixture; classifying the mixture to prepare toner particles, wherein thenon-linear polymer A, the linear polymer B and the polymer C comprise apolymer unit of the same kind.
 21. The method according to claim 20,wherein the release agent has a volume average particle diameter of from10 to 800 μm before mixed with the polymers A, B and C.
 22. A twocomponent developer comprising a toner composition and a carrier,wherein the toner composition comprises toner particles, said particlescomprising a binder resin and a release agent, and wherein when thetoner composition is pressed upon application of a pressure of 478kg/cm² to form a toner plate, the toner plate has surface having acoefficient of static friction of from 0.20 to 0.40.
 23. The twocomponent developer according to claim 22, wherein the toner particlesfurther comprise a magnetic material, and wherein the carrier is amagnetic carrier.
 24. Atoner container containing a toner composition,said toner composition comprising toner particles, and said particlescomprising a binder resin and a release agent, wherein the tonercomposition is pressed upon application of a pressure of 478 kg/cm², thetoner plate has a surface having a coefficient of static friction offrom 0.20 to 0.40.
 25. A developer container containing a two componentdeveloper comprising a toner composition and a carrier, wherein thetoner composition comprises toner particles, said particles comprising abinder resin and a release agent, and wherein the toner composition ispressed upon application of a pressure of 478 kg/cm², the toner platehas a surface having a coefficient of static friction of from 0.20 to0.40.
 26. An image forming apparatus comprising: an image bearing memberconfigured to bear an electrostatic latent image; an image developerconfigured to develop the electrostatic latent image with a developercomprising a carrier and a toner composition to form a toner image onthe image bearing member; an image transferer configured to transfer thetoner image on a receiving material optionally via an intermediatetransfer medium; and a fixer configured to fix the toner image on thereceiving material upon application of heat and pressure, wherein theimage forming apparatus has a waiting period not longer than 15 seconds,a maximum electric power consumption not greater than 1.5 KW when imageforming operations are performed and a maximum power consumption notgreater than 30 W when image forming operations are not performed, andwherein the toner composition comprises toner particles, said particlescomprising a binder resin and a release agent, and wherein when thetoner composition is pressed upon application of a pressure of 478kg/cm² to form a toner plate, the toner plate has a surface having acoefficient of static friction of from 0.20 to 0.40.
 27. The imageforming apparatus according to claim 26, wherein the waiting period isnot longer than 10 seconds.
 28. The image forming apparatus according toclaim 26, further having an image forming speed not less than 30 cpm/A-4size.
 29. The image forming apparatus according to claim 26, wherein thefixer comprises: a fixing roller A having a heater therein andconfigured to heat the toner image on the receiving material whilecontacting the toner image; and a fixing roller B optionally having aheater therein and configured to nip the receiving material to thefixing member A, wherein the fixing roller A has a thickness of 0.7 mm,and a pressure not greater than 1.5×10⁵ Pa is applied to the fixingmembers A and B.
 30. The image forming apparatus according to claim 26,wherein the fixer comprises: a fixing member configured to heat thetoner image on the receiving material while contacting the toner image;a fixed heater configured to heat the fixing member; and a pressuremember configured to press the receiving material to the fixing member,wherein the fixing member is at least one of a belt and an endless belt.31. The image forming apparatus according to claim 26, furthercomprising the toner container according to claim
 24. 32. The imageforming apparatus according to claim 26, further comprising thedeveloper container according to claim
 25. 33. An image forming methodcomprising: forming a toner image on a receiving material; and passingthe receiving material through a nip between two fixing members A and Bwhile applying a pressure to the fixing members A and B to fix the tonerimage on the receiving material upon application of heat and pressure,wherein the receiving material contacts the fixing member A, and whereinthe toner comprises toner particles, said particles comprising a binderresin and a release agent, and when the toner is pressed uponapplication of a pressure of 478 kg/cm² to form a toner plate, the tonerplate has a surface having a coefficient of static friction of from 0.20to 0.40.
 34. The image forming method according to claim 33, wherein thefixing member A has a thickness of 0.7 mm, and wherein the pressure isnot greater than 1.5×10⁵ Pa.
 35. The image forming method according toclaim 33, wherein the fixing member A is at least one of a belt or anendless belt and is heated by a fixed heater.
 36. A developing devicecomprising: a developer bearing member having a magnetic fieldgenerating means therein and configured to bear a developer comprising amagnetic carrier and a magnetic toner composition while rotating; afirst regulation member configured to regulate the amount of thedeveloper supplied to the developer bearing member to form a developerlayer on the developer bearing member; a developer containing memberconfigured to contain the developer scraped by the first regulatingmember; and a toner containing member located adjacent to the developercontaining member and configured to supply the magnetic tonercomposition to the developer bearing member through an opening, whereinthe developer containing member comprises: a second regulating memberlocated on an upstream side from the first regulating member relative tothe rotating direction of the developer bearing member, and configuredto scrape the developer layer when a concentration of the magnetic tonerin the developer layer increases and the developer layer thickens, tocover the opening with the scraped developer to stop the supply of themagnetic toner composition from the toner containing member, and whereinthe magnetic toner composition comprises toner particles, said particlescomprising a magnetic material, a binder resin and a release agent, andwhen the magnetic toner composition is pressed upon application of apressure of 478 kg/cm² to form a toner plate, the toner plate has asurface having a coefficient of static friction of from 0.20 to 0.40.